1. Field of the Invention
The invention concerns a package for liquid materials that is made of plastic-coated cardboard folded and bonded into a hollow shape consisting of a roughly triangular prism on a cubical base, the package having a point at which a drinking straw can be introduced.
2. Description of Related Art
There are basically only two methods of providing a punched or stamped opening on a package for liquid materials at a point through which a drinking straw can be introduced. Each of these methods however depends on a supplementary manufacturing process.
The first method involves cutting or stamping an opening in the cardboard and then coating it on one or both sides to seal it until it is punctured with a drinking straw. This method is not possible however when the cardboard blank out of which the package is folded together is already coated with plastic. There remains of course the second possibility of stamping the cardboard with just enough force at the point at which the straw is to be introduced to weaken it so that the straw can perforate it readily. This approach is however very difficult. The die can not be allowed to penetrate the cardboard to the slightest degree because even the smallest opening would allow air to enter and liquid to escape. Avoiding this problem by sealing the perforated or stamped point with a strip of adhesive material is of course known, but this measure also involves problems. Gluing or bonding the strip onto the package requires an additional manufacturing stage. The strip may come off too easily or even not provide a tight seal. If, on the other hand, the point has not been stamped deeply enough, it can not be perforated with the straw, which will bend and become unusable, as happens frequently.